Atrial involvement and progression of sinus node dysfunction in non-senile patients: evidences from electroanatomic mapping and long-term follow-up

Purpose Sinus node inability or conduction disorders of its surrounding atrial myocardium cause sinus node dysfunction (SND). This study aimed to characterize right atrium (RA) substrates and long-term atrial lead performance after pacemaker implantation in non-senile SND patients. Methods Eighteen SND patients (53.3 +/- 9.6 years) controlled by 18 age-matched supraventricular tachycardia patients were consecutively enrolled. The P-wave amplitude (PWA) and P-wave duration (PWD) were measured on surface electrocardiography. Electroanatomic mapping was conducted to assess the bipolar voltage, complex signals, volume, and activation time of RA. Pacemaker implantation was performed in SND patients after mapping. Results Compared with controls, SND patients showed significant PWA reduction (0.13 +/- 0.02 vs. 0.16 +/- 0.04 mV, p = 0.017) and PWD prolongation (120.8 +/- 15.2 vs. 105.2 +/- 8.6 ms, p = 0.001). The RA endocardial voltage was lower (1.56 +/- 0.78 vs. 2.57 +/- 0.55 mV, p < 0.001) and activation time was longer (112.1 +/- 14.9 vs. 90.8 +/- 12.4 ms, p < 0.001) in the study group. Atrial lead was anchored at the lower atrial septum in one patient and failed in another due to extensive atrial scarring. During a median follow-up of 86 (57-88) months, one patient lost atrial capturing, and overall atrial sensing was significantly decreased (2.44 +/- 1.16 vs. 1.87 +/- 1.01 mV, p = 0.003). Conclusions Atrial involvement was proved and the process was progressive in non-senile SND patients, as demonstrated by diffused RA lower voltage, slower conduction, and the decrease of the atrial lead sensing.